Ultraljud hos svenska vårtbitare

Of the 10 Swedish species of bush crickets 9 stridulate with their elytra. The author recorded the songs of these species in their natural habitats, using instrumentation tape recorder and ultrasonic detectors. Song rhythm patterms and frequencies are presented for each species with comments on the ultrasonic components, audibility as a distance in the field with and without detectors etc. For 8 of the 9 stridulating species detectors seem to be necessary for efficient survey work and population studies in the field.

In 5 species differences found between the songs used in daytime and at night were analysed and discussed. The most important differences were found in species singing close to the ground (Platycleis denticulata, Metrioptera brachyptera, M. bicolor), whereas no corresponding difference was found in species singing from trees or high busghes (Tettigonia viridissima, Leptophyes punctatissima). The very intense songs heard at night have distinct and discrete tooth-pulses, while corresponding songs in daytime contain continuous sound waves and less conspicuous tooth-pulses in the file pulse-train. It is suggested taht this phenomenon could be something more than a mere influence of temperature on song rhythym. They could be adaptations to more efficient spread of sound waves under the acoustical conditions taht prevail above ground at night.